The two federal inquiries examining three gay marriage bills currently before the Parliament have attracted hundreds of thousands of public responses, mostly in favour of changing the law. Mr Kirby sat in front of the committee to give evidence alongside the former NSW premier Kristina Keneally, also a supporter of same-sex marriage.

Mr Kirby spoke of his personal experience, of the fact he would like to be able to marry his partner of 43 years, Johan van Vloten.

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''A loving relationship of tenderness, of gentleness and affection, and fidelity and support is a beautiful thing and anyone who would disrespect it is not a kind person,'' he said.

Australia, he warned, was falling behind other nations such as Portugal, Mexico and Argentina, where gay marriage is legal.One of the committee members, Liberal Senator Michaelia Cash, queried him about whether his belief in relationship equality extended only to same-sex couples, ''or are you saying that there should be equity and equality in relationships regardless, for example, of the number of people participating in that relationship?''

Mr Kirby responded that there was a very specific question before the committee.